The invention relates to a control system for a power lift, in particular for a power lift for the hitch of an agricultural tractor.
A known control system is described in John Deere 2140 tractor, Technical manual, TM-4373. Besides the control members and a selector lever for different regulating modes, this system includes a gate arrangement having a plurality of slots, one of which displaceably receives an operating lever which is connected to the control members. The operating lever is provided with a hande at the end which projects above the gate. The lever can be displaced by an operator located within the tractor cab. The operating lever acts by way of the control members on a shaft which operates a lifting and a lowering valve which controls a hydraulic cylinder which raises and lowers the hitch. Whether those links perform a lifting movement or a lowering movement, and the extent thereof, depends on the regulating mode determined by the position of the selector lever. If the selector lever is in a position for positional regulation, then the position of the control members and the operating lever precisely corresponds to the position of the links. If however, the selector lever is in a position for draft force regulation, then the position of the links corresponds to the force which acts on the hitch links. If the selector lever is in a position for hybrid regulation, then the position of the links is dependent on a mixture of the hitch position and the draft force. It would be desirable to be able to operate such a system from a position outside of the tractor cab.